2002 GMC Envoy Owner's Manual - Page 280

Driving with a Trailer CAUTION: If you have a rear-most window open and you pull a trailer with your vehicle, carbon monoxide (CO) could come into your vehicle. You can't see or smell CO. It can cause unconsciousness or death. See "Engine Exhaust" in the Index. To maximize your safety when towing a trailer: D Have your exhaust system inspected for leaks, and make necessary repairs before starting on your trip. D Keep the rear-most windows closed. D If exhaust does come into your vehicle through a window in the rear or another opening, drive with your front, main heating or cooling system on and with the fan on any speed. This will bring fresh, outside air into your vehicle. Do not use recirculation because it only recirculates the air inside your vehicle. See "Comfort Controls" in the Index. Towing a trailer requires a certain amount of experience. Before setting out for the open road, you'll want to get to know your rig. Acquaint yourself with the feel of handling and braking with the added weight of the trailer. And always keep in mind that the vehicle you are driving is now a good deal longer and not nearly as responsive as your vehicle is by itself. Before you start, check the trailer hitch and platform (and attachments), safety chains, electrical connector, lamps, tires and mirror adjustment. If the trailer has electric brakes, start your vehicle and trailer moving and then apply the trailer brake controller by hand to be sure the brakes are working. This lets you check your electrical connection at the same time. During your trip, check occasionally to be sure that the load is secure, and that the lamps and any trailer brakes are still working. 4-56